When Bud Spillane was a school superintendent in New Rochelle, N.Y., he had to deal with removing an elementary school teacher suspected of sex abuse. “It was pretty evident he had done something,” Spillane recalls. The biggest obstacle to removing him from the classroom? “Parents came out of the woodwork…against me,” he says. They loved the teacher, the afterschool time he put in, and the weekend trips he liked to take students on, so they fought to keep him in school. Later in Spillane’s career, while he was leading the Fairfax County Public Schools outside of Washington, he had a teacher’s attorney demand a public hearing in a dismissal action involving multiple instances of alleged sexual misconduct with students. It was a shrewd move; instead of letting the school board handle the action in a private executive session, the lawyer wanted to force children to testify in court. Several parents understandably refused to put their kids through that spectacle. Welcome to the complicated and ugly world of sexual abuse in schools.

School shootings like the one this week in Ohio happen very rarely, but they understandably generate a lot of media coverage. By contrast, sexual abuse in schools happens much more frequently, to the point where the allegations have to be particularly egregious in order to make headlines. Miramonte Elementary in Los Angeles caught the nation’s attention the other week when a teacher was charged with a series of grotesque acts involving more than 20 kids, including allegedly photographing blindfolded students and spoon-feeding semen to some of them in his classroom. (Remember that the next time someone tells you that there is no way bad teaching could persist in school year after year without being noticed.)

That teacher and two others at the school have been accused of sexual misconduct, leaving parents to wonder just how pervasive this problem is and why school districts seem to have to take such unusual measures to deal with it. The Los Angeles school superintendent John Deasy responded to the Miramonte scandal by removing the entire staff, janitors and cafeteria workers included, to other positions in the district as investigators look into the school’s culture of silence. News of this dramatic move wasn’t helped by reports that the Los Angeles school board had agreed to pay the alleged blindfolder $40,000 to drop his appeals and leave the district. A $40,000 payment seems nuts, but it was actually the most expeditious and cost-effective way the board could fire the teacher, who has pleaded not guilty to the charges.

Miramonte is an extreme case. More common are allegations of teachers sleeping with older students or groping younger ones. How common? There is no reliable central database, but according to a nationwide investigation by the Associated Press in 2007, 2,570 educators were found to have engaged in sexual misconduct between 2001 and 2005 and more than 80% of those cases involved children. That’s a lot, particularly when you consider that that total undoubtedly was not inclusive of all incidents. At the same time, there are more than 3 million teachers, the overwhelming majority of whom work hard and are as revolted by these acts as the rest of us.

Still, here’s the uncomfortable reality: people who want to molest children go where children are, and schools are an obvious place. After the last decade, anyone who is surprised that big institutions are vulnerable to sex-abuse scandals — think the Boy Scouts and the Catholic Church — just hasn’t been paying attention.

But what should alarm parents is not the likelihood that their child’s teacher is dangerous — that probability is almost negligible. Rather, it’s the lack of a systematic backstop against these problems. One California teacher is now on the run in Mexico after reportedly being investigated multiple times by different school districts and moving around between them. A story that made headlines in New York City recently involved a teaching aide who was accused of molesting kids after allegedly being removed from another school for the same kind of activity.

The 2007 AP investigation showed just how porous state procedures intended to screen out abusers really are. I was on the Virginia Board of Education back then, and the AP story prompted reviews of licensing procedures because it was clear that a significant number of licensed teachers had problematic backgrounds that should have been flagged. Other states responded similarly.

That’s good, but states still need to do more.

To make sure abusers cannot get teaching positions, statewide data systems — and a national clearinghouse that states participate in — are dependent on vigorous reporting of abusers. Yet abuse cases are frequently not reported for a variety of reasons, including a well-intentioned but flawed effort to protect victims from the trauma of public disclosure. Unfortunately, handling these issues “quietly” merely displaces the problem to another community. Repeat offenders are hauntingly common. Not too long ago people suspected of or even involved in abuse could still get a letter of recommendation — if they agreed to leave without a fuss. Thankfully, growing awareness of the repeat behavior is making practices like that rarer.

In the end parents should be vigilant but not paranoid. Communicate with your child, and if you suspect a problem, take action. If something doesn’t seem right, trust your instincts. If a school official dismisses your concerns without looking into them, the next step is to contact the police. But maintain perspective. The reports out of Miramonte are ghastly, and sexual abuse of students is not a marginal issue, but thankfully it’s far from the most prevalent problem facing American schools.

Rotherham is a co-founder and partner at the nonprofit Bellwether Education, a national non-profit organization which, among other activities, does paid consulting work for clients including school districts, charter schools, and educational organizations around the country. The views expressed are solely his own.